1. Field of the Invention
The present invention relates to a light divergence angle limiting apparatus and method for limiting the divergence angle of light entering a plurality of pixels, and a projection image display apparatus having a plurality of pixels which are made to correspond to a plurality of color rays.
2. Description of the Related Art
Conventionally, there is an image display apparatus for displaying an image by using a liquid crystal display device (hereinbelow, referred to as a liquid crystal panel) as an optical modulating device. Image display apparatuses for displaying a color image are broadly divided into two types; a single-panel type using a single liquid crystal panel, and a triple-panel type using three liquid crystal panels corresponding to three color rays of red (R), green (G), and blue (B). In an image display apparatus using the liquid crystal panels, for example, light emitted from a light source is spatially modulated by the liquid crystal panels and the modulated light is projected onto a screen or the like, thereby displaying an image. Image projection types include a front projection type for projecting an image from the front side of a screen or the like and a rear projection type for projecting an image from the rear side of a screen or the like. The types of liquid crystal panels include a transmission type which transmits irradiated light and a reflection type which reflects irradiated light.
Some single panel type image display apparatuses each using the above-mentioned liquid crystal panel have, for example, a structure using color filters (CF) of three colors of R, G, and B. In the structure using the color filters, since a large quantity of light is absorbed by the color filters, it is difficult to increase the brightness and the structure has a disadvantage that cooling has to be performed. For example, Japanese Patent Application Laid-open No. Hei 4-60538 and xe2x80x9cAsia Display ""95, p887xe2x80x9d disclose a single-panel type image display apparatus which is intended for solving the problems and has the structure in which condenser microlenses each disposed so as to face three pixels are arranged, the color rays of R, G and B are allowed to enter each microlens from different directions and condensed, and the outgoing rays from the microlens are allowed to enter pixels corresponding to the three color rays of R, G and B. In the image display apparatus having such a structure, light entering an area between pixels (black matrix area in which a TFT (thin film transistor) as a switching device for driving pixels is formed) can be also effectively utilized. The substantial aperture ratio is therefore increased and the brightness is accordingly increased. Since an image display apparatus of this kind is constructed by using a single liquid crystal panel having a microlens array in place of a color filter, it is also called a single-plate, microlens, and no-color filter type projection liquid crystal display apparatus.
In the single-plate, microlens, and no-color filter type projection liquid crystal display apparatus, generally, a metal halide lamp is often used as a light source for emitting light to a liquid crystal panel.
As described above, in the single-plate, microlens, and no-color filter type projection liquid crystal display apparatus, color rays of R, G and B are allowed to enter each microlens provided so as to correspond to three pixels from different directions, and the color rays condensed by the microlens are allowed to enter the corresponding pixels for R, G and B, thereby displaying a color image. When an incident divergence angle of light irradiating the liquid crystal panel is large, a color ray (for example, B ray) enters not only a B pixel but also a neighboring pixel (in this case, R pixel or G pixel) as what is called xe2x80x9cleakage lightxe2x80x9d, so that color mixture occurs. As a result, color purity of a display image is reduced and there is the possibility that the picture quality deteriorates remarkably. Consequently, the incident divergence angle of light entering the liquid crystal panel has to be limited as necessary.
Particularly, the bright line spectrum of the R color ray of a metal halide lamp generally used as a light source for emitting light irradiating the liquid crystal panel is narrower than that of R and B color rays so that the ratio of the G and B color rays entering the R pixel is higher. It causes a problem that the color purity of the R color ray decreases. In this case, the incident divergence angle of each of the G and B color rays entering the R pixel has to be limited. One of methods of limiting the incident divergence angle is a method of limiting only the incident divergence angles of the G and B rays except for the R ray. The conventional projection liquid crystal display apparatus, however, does not have the structure for limiting the incident divergence angle of a specific color ray but has the structure for commonly limiting the incident divergence angles of all of color rays. Consequently, in order to limit the incident divergence angles of the G and B rays, it is necessary to limit the incident divergence angle of the R ray, and it causes a problem such that the quantity of the R ray decreases.
The present invention has been achieved in view of the above problems and it is a first object to provide a light divergence angle limiting apparatus and method capable of preventing unnecessary color rays except for a predetermined color ray from entering a pixel corresponding to the predetermined color ray.
A second object of the invention is to provide a projection image display apparatus capable of improving color purity and displaying a high-quality image by preventing unnecessary color rays except for a predetermined color ray from entering a pixel corresponding to the predetermined color ray.
A light divergence angle limiting apparatus of the invention comprises divergence angle limiting means into which light including a plurality of color rays comes and which limits a divergence angle of at least one of the plurality of color rays so that color rays different from a predetermined color ray do not enter a pixel corresponding to the predetermined color ray.
A light divergence angle limiting method according to the invention receives light including a plurality of color rays and limits the divergence angle of at least one of the plurality of color rays so that color rays different from a predetermined color ray do not enter a pixel corresponding to the predetermined color ray.
Further, a projection image display apparatus of the invention comprises: a light source which emits light including a plurality of color rays; light divergence angle limiting means to which light including a plurality of color rays emitted from the light source comes and which limits a divergence angle of at least one of the plurality of color rays so that light rays different from a predetermined light ray do not enter a pixel corresponding to the predetermined color ray; an optical modulating device in which a plurality of pixels corresponding to the plurality of color rays are arranged and which selectively modulates color rays entering the plurality of pixels in accordance with an image to be displayed; and projecting means for projecting each of the color rays optically modulated by the optical modulating device.
In the light divergence angle limiting apparatus and method according to the invention, light including a plurality of color rays comes in and the divergence angle of at least one of the plurality of color rays is limited so that color rays different from a predetermined color ray do not enter a pixel corresponding to the predetermined color ray.
In the projection image display apparatus according to the invention, the divergence angle of at least one of the plurality of color rays included in the light emitted from the light source is limited by the light divergence angle limiting means so that color rays different from a predetermined color ray do not enter a pixel corresponding to the predetermined color ray. The color rays entering the plurality of pixels are selectively optically modulated by the optical modulating device in accordance with an image displayed. Each of the color rays optically modulated by the optical modulating device is projected by the projecting means.
Other and further objects, features and advantages of the invention will appear more fully from the following description.